Jiyoung Lee

Multiscale vacancy and dislocation-mediated surface segregation in CuNi alloy up to microsecond timescales with accelerated dynamics - Volume 27 Issue S1

A novel n-octadecane/fumed silica phase change composite has been prepared as a building envelope with a high content of phase change material and improved energy efficiency. With a high porosity (88 vol%), the fumed silica provided sufficient space to impregnate a high quantity of n-octadecane (70 wt%). The composite exhibited high latent heat storage capacity (155.8 J/g), high crystallization fraction (96.5%), and a melting temperature of 26.76 °C close to that of pure n-octadecane. A 200 accelerated thermal cycle test confirmed good thermal reliability and chemical stability of the phase change composite. The thermal conductivity of n-octadecane was reduced by 34% after impregnation in fumed silica. A phase change composite panel was fabricated and compared to a commercial polystyrene foam panel. When used as the roof of a test room, the phase change composite panel more efficiently retarded heat transfer from a halogen lamp to the room and delayed the increase in the indoor temperature than that by the polystyrene panel. The indoor temperatures of the room with the phase change composite panel roof were 19.8 and 22.9 °C, while those with the polystyrene panel roof were 29.9 and 31.9 °C at 2200 and 9000 s after lamp illumination.

We present a facile approach to fabricate superamphiphobic surfaces by spray coating silica-fluoropolymer core-shell particles without substrate pretreatment with an additional binder resin. A series of SiO₂@poly(1H,1H,2H,2H-heptadecafluorodecyl methacrylate) (SiO₂@PFMA) core-shell particles with core particles of different sizes were prepared via thiol-lactam initiated radical polymerization (TLIRP). The surface of each SiO₂ particle with an average particle size of 12, 80, 150, and 350 nm was modified with (3-mercaptopropyl) trimethoxysilane and used as a seed for TLIRP. The SiO₂@PFMA particles with various SiO₂ sizes and contents were coated on aluminum substrates by a spray gun and then thermally treated to form a stable, rough composite layer. During the spray coating, the core-shell particles were aggregated by rapid evaporation of the solvent and then irregularly adhered to the substrate resulting in hierarchical structures. In the case of SiO₂@PFMAs with low SiO₂ contents, the roughness created mainly by the polymer shell disappeared during heat treatment. However, the substrates coated with SiO₂@PFMAs with high SiO₂ contents maintained the roughness even after heat treatment. The core-shell particles prepared with 12 nm SiO₂ formed a stable superamphiphobic surface. The water/hexadecane contact and sliding angles on an aluminum plate coated with SiO₂@PFMA, prepared using 12 nm silica at 46 wt% silica content (12 nm-SiO₂(46)@PFMA), were 178.5°/159.2° and 1°/7°, respectively. The cross-cut tape test showed that adhesion between the 12nm-SiO₂(46)@PFMA and the aluminum substrate was classified as 5B. A glass surface spray-coated with the core-shell composite particles exhibited transparent superhydrophobicity and translucent superamphiphobicity by controlling the concentration of the coating solution.